Effects of different degrees of acidity and concentration of bleaching agents on human enamel mineral content and surface morphology over time

Abstract

<p><strong>Objective</strong>: The aim of this study was to evaluate the effect of pH and concentration of bleaching agents on the mineral content and surface morphology of human dental enamel for 14 days. <strong>Material and Methods</strong>: Eighty human central incisors were randomly divided into 8 groups (n=10): G1-7.5% hydrogen peroxide/pH=9.0; G2–9.5% hydrogen peroxide/pH=9.0; G3-7.5% hydrogen peroxide/pH=7.0; G4-9.5% hydrogen peroxide/pH=7.0; G5-10% carbamide peroxide/pH=5.0; G6-16% carbamide peroxide/pH=5.0; G7-37% phosphoric acid 15s (positive control); G8-no treatment (negative control). The mineral analysis of the bleaching gel collected was assessed by ICP-AES and surface morphology was observed by SEM. <strong>Results</strong>: Friedman and Dunn’s statistical test demonstrated significant differences among the proposed treatments (p<0.01). No significant difference was found among groups treated with hydrogen peroxide (G1, G2, G3, and G4) or among groups G5, G6 and G7 (p>0.01). However, the latter groups showed significantly higher values as compared to groups G1, G2, G3 and G4 (p<0.01). <strong>Conclusion</strong>: Alteration in enamel mineral content may not be influenced by concentration when bleaching agents with the same pH are compared. The most apparent alterations in mineral content and surface morphology may be noted when more acidic products are used. The daily mineral content measurement may not be influenced by repeated applications of bleaching agents.</p><p> </p><p><strong>Keywords</strong></p><p>Dental bleaching; Mineral content; Enamel; Peroxide; Demineralization; pH.</p>

Effect of different methods of vital tooth bleaching on the resistance of enamel to erosion using Energy–Dispersive X-Ray Spectrometry analysis

“…EDS analysis showed a decrease in Ca % and P % values for all groups after the three methods of bleaching. The results were coincident with many other studies (45,51,52,61) . Even though 1% citric acid is not an ingredient of daily diet protocols; in vivo, it is considered a well-known and established method in erosion protocols in many studies (44,62,63) .…”

“…One of the main side effect of bleaching procedures is loss of mineral content of enamel which is related to the release and liberation of calcium and phosphorus ions as a consequence of dissolution of hydroxyl-apatite crystals (51) . This adverse effect may be attributed to the act of free radicals resulting from the oxidation of the inorganic and organic elements on teeth and the acidic pH of the bleaching material applied (35,52) .…”